Re: [PATCH] scsi: ufs: core: Avoid sleeping in hard interrupt context when PREEMP_RT is enabled.

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Low] The static function `ufshcd_intr` becomes unused when `CONFIG_PREEMPT_RT` is enabled, causing a compiler warning.
- [Low] Typo in the newly added source code comment.
--

commit 6afdc0b243918ce89eb55cea6349f608516d9d03
Author: Gregory CLEMENT <gregory.clement@bootlin.com>

scsi: ufs: core: Avoid sleeping in hard interrupt context when PREEMP_RT is enabled.

This commit addresses a sleeping-in-hard-irq context bug under PREEMPT_RT. 
It mitigates the issue by bypassing the hard IRQ handler and directly 
registering the threaded interrupt handler when PREEMPT_RT is enabled.

> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index d3044a3089b53..6d82658a1a66b 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -11235,9 +11235,17 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
>  	 */
>  	ufshcd_readl(hba, REG_INTERRUPT_ENABLE);
>  
> -	/* IRQ registration */
> +	/* IRQ registration
> +	 * In the case of PREMMP_RT, directly use the threaded

[Severity: Low]
This isn't a bug, but there is a typo in this comment ("PREMMP_RT" instead
of "PREEMPT_RT"). The commit subject also has a small typo ("PREEMP_RT").

> +	 * interrupt to avoid using a spinlock (which could sleep)
> +	 * in the hard IRQ handler.
> +	 */
> +#ifdef CONFIG_PREEMPT_RT
> +	err = devm_request_irq(dev, irq, ufshcd_threaded_intr, IRQF_SHARED, UFSHCD, hba);
> +#else
>  	err = devm_request_threaded_irq(dev, irq, ufshcd_intr, ufshcd_threaded_intr,
>  					IRQF_ONESHOT | IRQF_SHARED, UFSHCD, hba);
> +#endif

[Severity: Low]
Will this cause a compiler warning for an unused function when building with
CONFIG_PREEMPT_RT=y? 

Because the reference to ufshcd_intr() is compiled out in the #else block, 
but its static definition remains unconditionally compiled earlier in the 
file:

static irqreturn_t ufshcd_intr(int irq, void *__hba)
{
    ...
}

Could this break builds that have CONFIG_WERROR=y enabled due to the 
-Wunused-function warning?

>  	if (err) {
>  		dev_err(hba->dev, "request irq failed\n");
>  		goto out_disable;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260630-ufshcd-spinlock-sleep-fix-v1-1-339b05a1c6f4@bootlin.com?part=1